[MEDIUM] Bump @xmldom/xmldom to 0.8.15

[OskarEichler]

Summary

• raise the existing @xmldom/xmldom resolution floor from 0.8.13 to 0.8.15
• lock the Electron packager dependency to the fixed 0.8.15 release
• remain within the existing 0.8.x line

Security impact

Versions through 0.8.14 are affected by GHSA-6gmq-8vp8-gcm6, which permits XML fragment injection when an invalid EntityReference node name is serialized with well-formed output enabled.

Test Plan

• yarn install --frozen-lockfile --ignore-scripts
• yarn why @xmldom/xmldom confirmed 0.8.15
• yarn audit no longer reports the xmldom advisory
• yarn build
• debugger-shell: 4 suites, 9 tests, 4 snapshots passed
• XML parse/serialize compatibility check
• Jest retained a pre-existing open handle after reporting success and was stopped after completion
• git diff --check

Changelog:

[INTERNAL] [SECURITY] - Bump @xmldom/xmldom to 0.8.15.